Razors with pivoting blade units are well known in the art and, in fact, the concept extends back more than 50 years. The rationale behind the recent generation of pivoting cartridge razors is that when the razor is used the blade assembly responds to shaving forces pivots to provide a shaving angle of skin to blade which is constant throughout the shave. Examples of pivoting cartridge patents are set out below.
U.S. Pat. No. 3,938,247 to Carbonell, et al. issued Feb. 17, 1976 discloses a razor handle with a convex-concave combination which pivots in response to shaving forces when an otherwise stationary cartridge is attached.
U.S. Pat. No. 3,935,639 issued to Terry, et al. on Feb. 3, 1976 describes an arcuately convex cartridge which slides along mating guard rails attached to a concave extension of a razor handle. This assembly includes biasing means which directs the cartridge towards a "neutral" center position between the pivoting extremes.
U.S. Pat. No. 4,403,414 issued Sept. 13, 1983 to Kiraly and Ortiz describes a razor in which the handle forms a concave seat and the cartridge rotates within the seat.
U.S. Pat. No. 4,152,828 issued May 8, 1979 to Lund describes an off-center universal joint on the handle designed to mate with a suitable receptacle on a cartridge and is biased to automatically resume a neutral position between the extreme pivot range of the joint.
U.S. Pat. No. 4,253,235 issued to Jacobson on Mar. 3, 1981 describes cams disposed on journal arms extending outward from a razor handle for providing biasing action for a pivotal cartridge assembly.
U.S. Pat. Nos. 4,282,650 and 4,282,651 issued to Trotta on Aug. 11, 1981 describe a pivotal cartridge featuring a centrally mounted pivot bar which is attached to a razor handle by a sliding gate.
U.S. Pat. No. 4,057,896 issued Nov. 15, 1977 to Trotta discloses a razor cartridge which is joined to a razor handle by pivotal bearing means with the bearings positioned near either end of the bottom of the cartridge. Positioned between the pivotal bearing means on the cartridge is a complex cam surface consisting of two oppositedly inclined surfaces intersecting to form a dihedral angle. This cam is tracked by a cam follower on the handle which is biased by means of oppositedly disposed flexible cam arms positioned on either side of the central cam arm.
U.S. Pat. Nos. 4,083,104 issued Apr. 11, 1978 to Nissen and 4,026,016 issued May 31, 1977 also to Nissen disclose a razor cartridge such as that depicted in Trotta U.S. Pat. No. 4,057,896. Also disclosed therein is the configuration for the razor cartridge which have been commercially successful. This cartridge, rather than having the complex multi-faceted cam face of Trotta features a V-shaped profile with a flat surface which is engaged by a biased bullet shaped cam follower extending from the handle when the cartridge is attached. This combination along with others in the prior art utilizes the biasing force of a cam follower in a handle to direct the cartridge towards a neutral, i.e., center position between the extremes of the pivot arc formed by the cartridge during shaving. When the razor is removed from the face the force exerted against the bias is also removed and the orientation of the cartridge then returns to one in which the cam followers positioned in the joint of the V-shaped cam. This biasing center return is objectionable to many shavers who might otherwise prefer to change the cartridge orientation during shaving because there is no establishment of the changed orientation with a series of strokes. The user is, as a result, constantly positioning the razor against the bias rather than having once established a suitable shaving position having that position maintained throughout the shaving operation.